The invention relates to a bistable deflection element comprising an assembly of two plates which are provided with electrodes on both their principal surfaces and which are made of ferroelectric, easily polarizable ceramic material having a low coercive field strength. The plates are arranged with their principal surfaces one over the other and, are rigidly interconnected so that the inner electrodes are also electrically accessible.
The invention also relates to a method of manufacturing such a deflection element.
Unilaterally fixed ceramic deflection elements of polarized, ferroelectric ceramic material are normally deflected when a direct voltage is applied thereto, the deflection being approximately proportional to the applied electric voltage. This means that, when the voltage is interrupted, the zero position of the element is substantially reached again.
In many cases, for example, when ceramic deflection elements are to be used for switching purposes, it may be advantageous to maintain the switch positions of the deflection element after the interruption of the electric voltage; that is to say the deflection is maintained without a further electric voltage being required.
German Patent Application No. P 32 12 576.3 proposes a tristable optical switch in the form of a ceramic deflection element which comprises two plates of ferroelectric ceramic material which are uniformly depolarized in the initial position of the switch, i.e. in the "zero" position of the deflection element, while in the switching position each time one plate is polarized. This switch is depolarized via a decaying alternating voltage.
This switch has proven its worth in practice, but has the drawback that the generating of the decaying alternating voltage requires a certain technical effort.